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Old 07-23-2021, 07:10 PM   #1
Lt. Commander
Join Date: May 2014
Posts: 118
Default Loss of RPM

2002 Maxum SCR 3300. I have twin 350 Mag MPI. Engine drops 100 rpm's for a second then goes back to normal when running 600 to 1200 rmp"s. Staring to notice when engine runs 3000 rpm that engine will start slowing about 400 rpm Then maybe a few seconds, engine alarm coms on and drops about a hundred the back up to 3000. If I sit at dock with engine idle, it may be 10 seconds or maybe 3 minutes, alarm will come on and rpm's drop 100. seems like engine just quits and restarts itself because it is still running. Tried, new wires, plugs, rotor, and cap. Swapped out computer module, Idle Control Module, switched fuel hoses, replaced water filter. Had mechanic try engine computer hookup, said nothing shows. Said I need fuel pressure check and he didn't have with him. Got that and fuel was 43lb, and 39 when running. same on both engines. 2 boat mechanic couldn't find. first said I needed computer hook up, second did computer hook up, third was auto Mechanic and helped me check fuel pressure. Was good Trying to get another regular local boat Mechanic and he was 3 weeks out. Checked after 2 weeks and he said he is still far out to get to it. Hoping he can get to it soon. but still trying what I can do to possibly find and be able to boat

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Old 07-24-2021, 12:13 AM   #2
mmwjr's Avatar
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 9,594

Are you certain this isnít a bad tach issue? If alarm is sounding itís hard to believe there isnít any faults stored in the computer.

1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2

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Old 07-24-2021, 12:45 PM   #3
Lt. Commander
Join Date: May 2014
Posts: 118

Tach works good, engine actually slows. Ran on small trip yesterday. ran fine. Got to dock and docked with no problems at all. Engine kept rpm's. Shut down and started about 5 minutes later to check, and it was back to cutting out and doing the same as before. I couldn't believe nothing showed. Having another mechanic check, hopefully this Monday or Tuesday
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engine problem, rpm problem. please

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